My professor showed me a kaong sugar cube. It was white, as white as freshly harvested kaong sap. It was a trial processed using microwave oven.
That make sense. If the processor is after the color quality, a microwave energy might be perfect. In small to large scale, this can be done by passing a very thin film under microwave heated tunnel.
A very expensive and slightly risky method. Microwave consumes huge amount of power that equates to huge electric cost. The risk factor – it boils anything with water. Human body is 70% water. This idea is only feasible if someone can source a very low cost electricity and can construct a safe equipment.
Anyway, I was curious so I did a simple test on guyabano leaves.
The idea is heat the leaves as high as possible using the least amount of time. I heated five leaves separately at maximum heat setting but varied the time with each test.
Trial 1. Max heat for 5 minutes.
Trial 2. Max heat for 4 minutes.
Trial 3. Max heat for 3 minutes.
Trial 4. Max heat for 2 minutes.
Trial 5. Max heat for 1 minute.
Leaves color never had any changes in any trials, before and after microwave heating. No color changes were observed in between trials either.
Each leaf was crumpled after heating. Three to five minutes heating period rendered the leaves very brittle while 1 to 2 minutes only made them slightly brittle. The drier the sample becomes, the more brittle it becomes. Microwave can heat the sample as long as it has moisture. Heating stops as soon all moisture is almost evaporated. I think microwave heating a single leaf for three minutes at maximum heat setting is sufficient.
Note: heating several leaves at the same time will surely give different quality.